feat: Allow secret functions to use public parameters

[jfecher]

Related issue(s)

No formal issue but resolves an issue in example 1.3 of the noir-aztec3-examples.

Description

Summary of changes

Allows 'secret' functions in contracts to take public parameters and have public return values.

With this the generated abi for the file looks like the following. (... marks omitted lines)

{
  "name": "PrivateToken",
  "functions": {
    "constructor": {
      "func_type": "secret",
      "function": {
        "circuit": [
            ...
        ],
        "abi": {
          "parameters": [ ... ],
          "param_witnesses": {
            "call_context": [1, 2, 3, 4, 5, 6],
            "contract_deployment_data": [7, 8, 9, 10, 11],
            "value": [12],
            "owner": [13, 14]
          },
          "return_type": {
            "kind": "struct",
            "fields": [...],
          },
          "return_witnesses": [15, 15, 15, 15, 15]
        }
      }
    }
  }
}

Dependency additions / changes

Test additions / changes

Checklist

• I have tested the changes locally.
• I have formatted the changes with Prettier and/or cargo fmt with default settings.
• I have linked this PR to the issue(s) that it resolves.
• I have reviewed the changes on GitHub, line by line.
• I have ensured all changes are covered in the description.

Documentation needs

• This PR requires documentation updates when merged.

Once contract functions are documented, we'll need to also document that secret functions (the default) can use pub parameters and their return values must also be pub. They cannot use pub if they are also unconstrained.

Additional context